Piston



Feb. 5, 1946.

J. w. HOWLETT PISTQN Filed March 20', 1945 Patented Feb. 5, 1946 PISTON John William Howlett, Lymington, England, as-

slgnor to Wellworthy Piston Rings Limited,

Lymington, England Application March 20, 1945, Serial No. 583,697 In Great Britain December 1, 1944 8 Claims.

This invention relates to a piston, for use in a cylinder bore (for example, the bore of a cylinder block, liner or valve sleeve), of the kind havin a skirt formed of an alloy having a greater coefiicient of expansion than that of the material (usually cast-iron or steel) of the cylinder. the

skirt being provided with at least one longitudinal 'slit extending fully or mainly throughout the length of the skirt.

A piston of which the skirt is formed of a light alloy having a relatively-high co-emcient of expansion has normally to be provided with a relatively-larse working clearance as regards the owlinder bore in which it is intended to work, and the longitudinal slitting oi the piston skirt is eifected with a view to reducing the working clearance.

But it has alternatively been proposed, with a view to further reducing the working clearance which is necessary, to provide the skirt of such a piston with a sheath or sleeve of a material having a co-efilcient of expansion less than that of the piston skirt, which sheath or sleeve is secured in a groove of the latter by welding or brazing to one or more inserts provided in aper tures in the piston skirt, so that the exterior periphery of the sheath or sleeve is capable of making contact with the wall of the. cylinder bore.

I light alloy of the piston and the inner periphery 1 of the ring, as the light alloy cools during the casting operation, which naturally militates ainst the success of the ring in controlling the.

skirt expansion. The avoidance of such clearance involves'very considerable production difficulties. Y

The main object of this invention is to provide a piston of the kind first specified with which the working clearance can be further reduced in a very simple manner, and without production difllculties being encountered.

A further object is to arrange a skirt-control ring so that the permitted expansion of the skirt.

when the piston has been well run in, can be varied, as desirable, in a simple manner.

According to the invention the skirt of a piston,

of the kind first specified, has a portion the external periphery ofv which is machined and has mounted thereon from the open end of the skirt a non-split ring which has a co-efilcient of ex- 1 pansion less than that of the skirt, and preferably comparable to that of the cylinder, and which coacts with the said machined periphery to control the outward expansion of the skirt.

In the accompanying drawing:

Figure 1 is a halt elevation of a piston provided with a skirt-control ring according to the invention;

Figure 215 a full sectional elevation thereof taken along the line II-II of Figure 3;

Figure 3 is a halt cross-section taken on the line III-III of Figure 2; and

Figure 4 is a full cross-section taken on'the line IV-IV of Figure 2.

In the construction shown the head 12 is formed with a number of external grooves for piston rings in an ordinary manner, and the skirt [3 is partially severed from the head by means oi a slit N, which, it will be observed, extends over one of the pressure faces of the piston. A longitudinal slit ii in the skirt extends from the open end l6, remote from the-head l2, to a point approximately mid way ofthe ends of the slit it. The gudgeon pin bosses l! are integrally attached to the head by means of lugs l8 and Webs 19, being separated from the skirt, remote from the head, by slits 20, 20. In addition, the bosses are connected to the interior surface of the skirt by relatively-fiexible, integral webs 2 l 2 i, the webs being attached internally to the pressure faces of the skirt. I

' In the present instance the skirt is provided interiorly, on the side of the gudgeon pin bosses remote from the head, with a belt 22 of metal which is machined from the open end of the skirt-to provide aninternal, axially-extending flange 28 directed towards the open end, and itis with the external periphery of this flange that the restraining or control ring 24 coasts. The latter may be fitted (though it need not be) as a slight interference fit, and if so fitted the open end of the skirt can be held contracted in any convenient manner whilst. the restraining ring is being fitted.

It'is preferred to provide a detachable means for axially locating the ring 24. At one end it a can be axially located by the adjacent wall 26 of the skirt from which the flange '23 extends, and at its other end by means of a spring ring 21 mounted mainly within the flange 23 and having projections or bulges 28 which extend through secure by Letters Patent the United States is:

1. A piston, for use in a cylinder bore, having a skirt formed or an alloy having a greater coeflicient of expansion than that of the material of the cylinder, the skirt being provided with at least one longitudinal slit extending mainly throughout the length of the skirt, the skirt having a portion the external periphery of which is accessible from the open end of the skirt, and a non-split ring mounted on said external periphery and serving to' control the outward expansion 01 the skirt, said ring having a coeflicient of expansion less than that of the skirt,

2. A piston cast of a light alloy and provided with at least one longitudinal slit extending mainly throughout the length of the piston skirt, the latter having internally of its outer surface a portion the external periphery of which is accessible from the open end of the skirt, and a non-split ring mounted on said external periphcry with a slight-interference fit, said ring having a coeillcient oi! expansion less than that of the skirt.

3. A light-alloy piston provided with at least one longitudinal slit extending mainly throughout the length of the piston skirt, wrist pin bosses rigidly connected with the piston head, the skirt having internally of its external periphery and between said wrist pin bosses and the open end or the skirt an integral flange' extending axially towards the open end of the skirt, and a nonsplit ring mounted on said flange, said ring having a coefllcient or expansion less than that of the skirt and serving to control the outward exadjacent its open end, a flange extending axially towards and accessible from the open end of the skirt, a non-split ring, having a coefllcient of expansion less than that of the skirt, detachably mounted on said flange to control the outward expansion of the skirt, and a detachable means providing axial location for said ring.

' 5. A piston provided with at least one longitudinal slit extending mainly throughout the length of its skirt, the latter having internally, adiacent its open end, a flange extending axially towards and accessible from the open end 01 the skirt, a non-split ring, having a coefflcient of expansion less than that of the skirt, detachably mounted on said flange to control the outward expansion of the skirt, and a detachable means providing axial location for said ring, said detachable means in the form of a spring ring mounted internally of said flange and having a p urality of projections extending through slots in said flange.

6. A piston having a skirt, a head, wrist pin bosses rigidly connected wtih said head, the skirt being formed interiorly, between said wrist pin bosses and its open end, with a flange extending axially towards and accessible from the open end of the skirt, and a non-split ring, of a material having a coemcient or expansion which is less than that o! the skirt, detachably fitted on said flange to control the outward expansion of the skirt.

7. A piston having a skirt, a head, wrist pin bosses rigidly connected with said head, the skirt being formed interiorly, between said wrist pin bosses and its open end, with a flange extending axially towards and accessible from the open end of the skirt, a non-split ring, or a material having a coefllcient of expansion which is less than that of the skirt, detachably fitted on said flange to control the outward expansion 0! the skirt.

and a spring ring mounted internally or said flange, said spring ring having projections extending through slots in said flange to provide 0 axial location for said non-split ring.

8. A light-alloy piston or which the skirt is formed interiorly, near its open end, with a flange extending axially towards and accesible from the open end, of the skirt, and a non-split ferrous ring detachably fitted on said flange.

JOHN WILLIAM HOWLEI'I.

@eificete of @erre f I Patent No. 2,394,241. February 5, me.

- JOHN WILLIAM HoETT is hereby certified that the above numbered patent was erroneously issued to Wellworthy Piston Rings Limited, of L should have been issued to the inventor said Hewlett and Wellworthy Piston Rings mington, England" whereas said patent Limited,- of Lymington, England, assignee of one-half interest therein, as shown by the record of assignments in this ofiice; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 21st day of May, A. D. 1946.

[SEAL] LESLIE FRAZER,

First Assistant Commissioner of Patents. 

